Under low voltage, high load conditions, (Similar to those conditions commonly found in typical RV applications), air conditioning and heat pump systems can cause circuit breakers to trip thereby shutting down the entire electrical circuit until the circuit breaker is manually reset. Further, conventional variable speed control systems having a variable speed compressor arise in applications for heating or cooling buildings where there is an unlimited supply of current to operate the compressor. However, a problem arises in RV applications. In RV applications the total available current is limited thus the user must turn off the heating/cooling system if there is not enough current to operate the compressor. This results in poor heating/cooling efficiency and control. Thus, what is needed is a heating and cooling system having a variable speed compressor for an RV where the incoming current and voltage of the compressor can be monitored and controlled. By monitoring the incoming current and voltage on the electrical circuit, the variable speed control system can control the input to the variable speed compressor, allowing the compressor to vary its output to assure that the incoming power limitations are not exceeded.